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RESEARCH PRODUCT

Influence of Guideline Operationalization on Youth Activity Prevalence in the International Children's Accelerometry Database

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Introduction: The United Kingdom and World Health Organization recently changed their youth physical activity (PA) guidelines from 60 minutes of moderate-vigorous PA (MVPA) every day, to an average of 60 minutes of MVPA per day, over a week. The changes are based on expert opinion due to insufficient evidence comparing health outcomes associated with different guideline definitions. Further, inconsistent guideline operationalization impairs understanding of physical inactivity prevalence. This study used the International Children’s Accelerometry Database to compare approaches to calculating PA compliance among youth and associations with health indicators. Methods: Cross-sectional accelerometer data for 21,612 youth (5-18y) was used to examine compliance with four guideline definitions: daily method (DM; ≥60 minutes MVPA every day), average method (AM; average of ≥60 minutes MVPA per day), AM5 (compliance with AM and ≥five minutes of vigorous PA [VPA] on ≥three days), AM15 (compliance with AM and ≥15 minutes VPA on ≥three days). Associations between compliance and health indicators were examined for all definitions. Results: Compliance varied from 5·3% (DM) to 29·9% (AM). Associations between compliance and health indicators were similar for AM, AM5, and AM15. For example, compliance with AM, AM5, and AM15 was associated with a lower BMI z-score (statistics are coefficient [95% CI]): AM (-0.28 [-0.33,-0.23]), AM5 (-0.28 [-0.33,-0.23], AM15 (-0.30, [-0.35,-0.25]). Associations between compliance and health indicators for DM were similar or weaker, possibly reflecting fewer DM-compliant participants with health data (n=250-1,127) and lower variability in exposure/outcome data. Conclusion: Youth who complete 60 minutes of MVPA every day do not experience superior health benefits to youth who complete an average of 60 minutes of MVPA per day. Guidelines should encourage youth to achieve an average of 60 minutes of MVPA per day over a week. Different guideline definitions impact inactivity prevalence estimates; this must be considered when analyzing data and making cross-study comparisons.